The Use of the Wien Bridge for the Measurement of the Losses in Dielectrics at High Voltages, with Special Reference to Electric Cables

Abstract

In the preliminary section, the loss angle of an imperfect condenser is defined, the equations for the Wien bridge are derived, and the effects of variations of frequency and voltage on the balance are discussed. One of the difficulties in the application of large potential differences to a bridge is the effect on the arm which has to withstand the high voltage. In the arrangements due to Monasch and Schering, this arm is the known condenser; in the bridge as used by the author, the voltage is applied to the ratio coils. The errors introduced by earth impedance are eliminated by using the Wagner auxiliary bridge. The applications to measurements on cables are considered, and the use of the double bridge in determining the wire-to-wire and wire-to-sheath losses in a multi-core cable is described. In Appendix I. the corrections due to imperfections of the bridge arms are discussed, and in Appendix II. a simple quantitative theory of the double bridge is given.